The present invention relates to monitoring a mobile network, and more particularly to a method of performing a multi-protocol call trace on General Packet Radio Service (GPRS) Gb-Gr interfaces of a Global System for Mobile communications (GSM) network.
GPRS is a standard from the European Telecommunications Standards Institute (ETSI) on packet data on mobile communications networks. By adding GPRS functionality to the Public Land Mobile Network (PLMN) operators give their subscribers access to external Internet Protocol-based (IP) networks. GPRS introduces two new nodes for handling packet traffic, as shown in FIG. 1: a serving GPRS support node (SGSN) and a gateway GPRS support node (GGSN). These nodes interface with a home location register (HLR), a mobile switching center/visitor location register (MSC/VLR) and base station subsystems (BSS). The GGSN is coupled to the SGSN via an IP backbone, and the SGSN is coupled to the BSS and resides at the same hierarchical level in the network as the MSC/VLR. The SGSN keeps track of the location of the GPRS user, performs security functions and handles access control, i.e., it does for the packet data service (PDS) what the MSC/VLR does for the circuit switched service (CSS). A Gb interface regards the communication between the BSS and the SGSN, while a Gr interface regards the communication between the HLR and the SGSN.
As an example the Gb interface carries both signaling and payload messages. The signaling is related to the “signaling plane” and the payload is related to the “user plane.” The layout of the user plane is shown in FIG. 2 and the layout of the signaling plane is shown in FIG. 3. The protocols to be evaluated are the frame relay (FR), network service (NS), base station system GPRS protocol (BSSGP), the logical link control (LLC) and the GPRS mobility management and session management (GMM/SM).
Generally the requirements for call trace include tracing GPRS procedures on the Gb and Gr GPRS interfaces, with both real time and off-line GPRS procedure trace needed. The procedure trace on GPRS is applied network wide on all the GPRS Gb logical links and Gr signaling links available in the system. The user may view together the Gb and Gr results, if monitoring of these interfaces is available.
In GPRS networks, as well as the previous GSM networks, there is a deep interaction between different network entities throughout the network. Basic features, such as packet switched mode and increased transfer speed, mobility, roaming radio resource sharing, etc., have to be controlled and measured to assure a good quality of service (QOS) to subscribers. One main problem that network operators have to solve is the control of the network and the ability to check specific problems in each network interface as well as network wide. For example the subscriber may complain: “Yesterday I wasn't able to get the GPRS service working” or “One hour ago my GPRS file transfer had a terribly slow transfer rate.” The operator has to provide a reason why the service wasn't available and check the problem in the network, taking into account all the network entities that may be significant in the process, such as the cell, the BSS, the SGSN, the HLR, etc. To accomplish this the operator needs to store the GPRS Gb and Gr data of the network for a period of time, to analyze the stored GPRS data in a fast, easy way to get information about subscriber activity, to correlate Gb and Gr transactions as well as GPRS and GSM transactions and calls network wide, to analyze the GPRS Gb and Gr traffic in real time, and to display the results with different levels of detail.
The straight forward way to have a multi-protocol procedure or call trace on GPRS is to store every packet data unit (PDU) from probes located at monitoring points in a centralized system and on demand from a user-client get the stored PDUs and decode and process them according to a trigger. The multi-protocol correlation may be done with more post-processing elaboration on the results of the previous process. However this is not a fast, easy way to get the results of the procedure trace for the user. The problems of this approach are the bandwidth needed to get everything in a centralized repository and the extremely slow decoding process on huge amounts of PDUs. With this approach the results of a procedure trace applied on one day of GPRS data may be available after one day of processing.
What is desired is a fast, easy way to perform procedure trace on GPRS data without involving a lot of bandwidth while allowing correlation of GPRS and GSM results.